Photo Editing

It is perfectly possible to print or publish photos from your digital camera without making any further adjustments to the image, but to really make the most of your photos it is worth spending some time processing them. There are many image processing packages on the market, ranging from free open-source software all the way up to very expensive systems aimed at professionals and serious enthusiasts. Any software package should be capable of performing the basic editing functions described on this page.

Before editing your picture – even as simple an operation as turning it from horizontal to vertical – you should make a copy of your original. For one thing, it is always possible that your computer will crash or the power fail whilst saving your edited copy, and if you are overwriting the original then it may be lost for ever. But in addition to that risk, it is a general principle that every time you save a photo in a compressed ‘lossy’ format such as JPEG, some image deterioration takes place. It is always good to have the original available to provide maximum definition should you want to reprocess your photo at a later date.

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Cropping

Sometimes, despite your best efforts at composing your photo, you will notice intrusive features at the edges of the picture, or imbalances in the positions of important elements. Sometimes you may simply need to adjust the proportions of your photo in order to fit a particular frame, or for aesthetic reasons. And sometimes you may find that you just want to enlarge a portion of your photo.

All packages will allow you to crop your photo by dragging a rectangular selector around the area you want to keep. If you are intending to print your photos, or present them together in an online gallery, then it may be a good idea to use a consistent aspect ratio when choosing an area to crop – in other words use the same proportions for all your images. Many cameras produce photographs with a 4:3 or 3:2 aspect ratio, these are quite pleasing to the eye. A square crop has a quite different feel to it – experiment with this format too.

If you are intending to crop your photo to use it as your computer desktop background or wallpaper, you should try to choose dimensions that exactly match your monitor’s resolution – for example 1024×768, or 1280×1024 pixels. That way the image does not need to be rescaled for display and so will be shown with maximum clarity.

White balance

The human eye and brain are very good at deciding on the true colour of an object even when it is illuminated by an off-white light source. Various types of artificial light used indoors can have a noticeably different tint compared with sunlight or flash, and all digital cameras have settings to compensate for this in order to produce realistic-looking colours in a photograph taken under a range of conditions. However sometimes the camera will make a wrong guess at the type of lighting, or you will forget to select the appropriate manual white-balance setting, and the photo will end up with an unnatural colour cast to it.

Image processing packages normally have an option to adjust the white balance of an image. In order to work correctly, the software needs to identify a region that should appear as a shade of grey – sometimes you will have to manually select such an area, and sometimes the software will take the brightest area in the picture and assume it is a direct reflection of the light source. It will then adjust the colours in the photo to compensate for the presumed colour of the light source. If the result doesn’t look correct then you should be able to manually override the settings, often by choosing a ‘colour temperature’. Technically, this represents the temperature of an object that would glow with a particular colour of light – a temperature of 5500K may be used for sunlight, 6500K may be used for white daylight, 2700K for the warm colour of a filament bulb, and 9000K for the bluish light of some video monitors. You can tell the software what was the colour temperature of the light source in your photograph, and it should adjust the photo appropriately.

Note that if you have mixed light sources then it can be very difficult, if not impossible, to correct for them in the final picture – a portrait of someone lit by daylight through a window but also with indoor lighting will likely have an unnatural colour cast on one side or the other of the subject. You should avoid mixed light sources if possible, unless done deliberately for artistic effect.

Black & white conversion

Most digital cameras have the ability to store photos in black and white, but it provides more flexibility to shoot in colour and convert to black and white afterwards – that way you can still use the colour photo if you decide that you prefer it to the monochrome version. Photo editing software will usually offer a simple menu option to convert a picture to black and white, but you may find the results can be improved by increasing the contrast a little afterwards – monochrome prints tend to have darker shadows and lighter highlights than colour prints, and can look more striking as a result.

An alternative conversion method that may be available in your editing software is the channel mixer. All the colours in a photo are made from varying proportions of the primary colours, red, green and blue. Using the channel mixer you can create a monochrome (sometimes called greyscale) image where the brightness of each pixel is made from a blend of the primary colours that you control with three sliders. So for example, if you set the red slider to 100% and the green and blue to zero, then the monochrome result will be white where the original image was bright red, and black in any areas where there was no red component, including areas that were bright blue or green. Setting the sliders to 50% red, 50% green, 0% blue would make a blue sky appear quite dark in the monochrome result, but green foliage and red or yellow flowers would appear in shades of grey. In general you should make the three sliders add up to 100% – if the total is less than this then the highlights in your image will appear grey which looks unnatural, and if the total is more than 100% you run the risk of creating large ‘blown’ highlight areas where there is no detail. As always, though, you are free to use any values that work for you artistically.

Contrast, brightness, and saturation

Sometimes a photograph can benefit from a bit of adjustment to its overall contrast, brightness or saturation. Contrast refers to the distinction between light and dark areas – increasing contrast will make shadows deeper and highlights brighter, whilst decreasing it will make everything tend towards a neutral grey colour.

Brightness, as its name suggests, adjusts the lightness of your image by adding or subtracting the same amount from every pixel – increasing brightness makes the image tend towards a white color, decreasing it tends towards black.

Saturation refers to the intensity and purity of colours in the image. Reducing saturation gives the photo a muted pastel-coloured appearance, tending towards a monochrome image when saturation is reduced to zero. Increasing saturation makes colours seem more vivid. In general, saturation can be reduced as much as you like, but you probably shouldn’t increase it too much as the result can become rather garish.

Cloning and Object Removal

Occasionally you will find a photograph that could be improved greatly by removing or changing a small distracting element - for example, a fly on somebody’s face, or an intrusive branch on the edge of a landscape, or a speck of dirt on the camera lens. Usually in a case like this it is possible to ‘fix’ the photo using the clone tool n your image editing software.

Cloning is simply the act of copying one portion of an image into another location, obscuring what used to be there. If the blemish that you want to remove is in an area which is visually similar to another portion of your photo then you can copy from the unblemished area over the spot you want to erase. This can be quite effective if the background is something textured, such as grass or foliage, provided you choose a source area where the texture is similar in scale as well as colour. Erasing objects over large scale backgrounds, such as buildings, can be more tricky to do well because you need to accurately match any edges that traverse the region being edited. Objects on smooth background with a colour gradient, such as a blue sky, may be better treated with an ‘object removal tool’ if your software has such a thing, since it is often difficult to match a gradient accurately.

In use, a clone brush requires you to first specify the source of the clone operation – this is the location on the image (possibly another image) from which pixels will be copied. You should set the size of the clone brush to be similar to or smaller than the object being removed, and give the brush a fair amount of ‘softness’ so that the edges of the copied area blend in with the background you are replacing. Then use the brush to ‘paint’ the new background over the blemish.

There are a few things to watch out for when cloning, in order to produce as realistic a result as possible. Try not to pick the source too close to the destination, and in particular don’t allow the cloning operation to draw over any areas that will also be used as source pixels. If this happens you will find obvious repeating patterns in the result, which look unnatural and distracting. Try also not to pick a source that includes obvious elements that stand out to the eye, such as large branches, or differently coloured patches of grass – if these shapes occur more than once in an image it will be very apparent that you have used the clone tool. Sometimes it may help to use more than one source location, and perform the cloning in several steps so as not to use too much of any one area of background. 

Resizing

Most digital cameras produce images which are several thousand pixels across. If you are going to print your photo then you should not resize it before sending it to the printer – the printer setup page will allow you to specify the physical dimensions for your print and will perform any necessary scaling internally. However if you are going to display your photo electronically – on a webpage, digital photo frame, desktop background – then for best results you should generally resize the image before displaying it, so that it has the same pixel dimensions as the device it will be shown on.

When downsizing (shrinking) an image, several image pixels (and maybe parts of pixels) will be merged into each output pixel. If possible it is a good idea to shrink by an exact fraction such as 1/2, 1/3, etc. so that pixels do not end up being effectively ‘split’ between two output pixels, since this causes a degree of blurring. So if you are both cropping and resizing your photo, then you should try to crop to a rectangle which is a multiple of the size you want to resize to.

You should avoid resizing the same image more than once, since each time you resize you lose some clarity. If you need several different otput resolutions you should generate each one individually from the highest resolution available. For example if your original is 3000×2000 pixels and you need a 900×600 and a 600×400 version, you should not create the 900×600 and then rescale that by 2/3 to make the 600×400 – instead you should scale the original by 1/5 to make the smallest image.

Unless your image editing software has trouble processing large images, it is nearly always best to perform as much processing as possible before resizing – the general workflow should be something like: Cropping -> Colour adjustments -> Cloning and Edits -> Resizing -> Sharpening -> (Optional framing) -> Publishing.

Framing

Many packages allow you to add decorative borders and frame effects to your photos. How or whether you use these is a matter of personal taste! A collection of photos presented with a consistent framing style can look quite striking, and drop shadows can be added to give the appearance that your photos are separate from the background page. You may also include copyright information on the frame or as an overlay on the image itself.

If you have specific image size requirements (e.g. an online gallery that needs 800×600 images) then remember to allow for the exact border dimensions when resizing your photos – if the border is 30 pixels wide then you will need to have resized your photo to 740×540 prior to adding the border. Note also that adding a fixed-width border slightly changes the aspect ratio of an image. 

Sharpness

Occasionally you will find a photograph looks a little soft, perhaps as a result of poor focusing, or after resizing in your image editor. If the softness is only slight then it is possible to improve the appearance by sharpening the photo. Sharpening works by measuring the changes in brightness between nearby pixels, and slightly boosting the changes so that edges become more emphasised – this fools the eye/brain into thinking that the image is more detailed than it actually is. Note that sharpening cannot restore detail that has been blurred away, but it can give a crisper appearance to an image. It is very important not to overdo sharpening – when applied to excess it gives a very artificial look to an image which can be quite uncomfortable to view – bright spots will be surrounded by small darker circles, and dark spots by bright circles. Similarly, you should never apply sharpening more than once. It is best left until the final stage of editing your photo, after you have resized it and when you are ready to save it for publishing or printing.

Photo Management

Organising your photographs on your computer in some way is vital if you are ever going to want to find a particular shot at some time in the future. You might simply store them in folders named with a timestamp and subject, but there is plenty of software available which can go further than that and make your life a lot easier.

Most photo management packages will perform a scan of your hard drive on installation, or designated areas of it, looking for photos to add to a library. They will also include various tools for browsing or searching the library, and adding new images to it. Often there will also be some ability to edit your pictures as well. 

You should check the manner in which the library is displayed, to see whether it suits your needs. Also check how easy it is to tag your photos with keywords to allow you to find them in future. It is also worth bearing in mind that is takes a considerable effort to tag and catalogue all the photos in your collection, so if you decide to change your photo manager at some time then ideally you’ll need to be able to export the database and transfer it to the new manager.

Online Galleries

Displaying your photos in an online gallery can be rewarding, as well as providing a convenient way to show them to freinds and family. Making your photos visible to a wider audience will encourage you to improve your photographic skills, and you may well find that people’s perceptions of, and comments on, your pictures can help you to see them in a different light.

Many online galleries exist - some are free and some require a small subscription. The free ones will often be supported by advertisements, which may be distracting to your viewers. The subscription galleries will usually offer much more control over layout, backgrounds, etc., allowing you to create a more professional-looking collection.

When choosing a gallery for your photos you should bear in mind that you might want to change provider in the future. It may be possible to download all your photos to transfer them to a new gallery, but it is likely to be easier to keep local copies – which also provide a backup if anything should corrupt the files in your online storage.

When uploading to your gallery, check what size the images will be displayed at and resize them accordingly as one of the last steps of your image processing. That way you will reduce the bandwidth and storage requirements for your image, and ensure the best display quality since the image will not need to be resized on the gallery server.

 

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